The Global Positioning System (GPS) or another global navigation satellite system (GNSS) provides location information to a receiving device anywhere on Earth as long as the device has a substantial line of sight without significant obstruction to three or four satellites of the system. Location-based services control features of an application based on location information from a GNSS or another source.
The increasing trend of smart phones and wide spread integration of GPS devices in vehicles lead to availability of large pool of user location data including stay-points, checkins and mobility traces. When such mobility data is aggregated in a centralized manner, it makes new applications such as traffic analysis and prediction possible. The aggregated and sharing of mobility traces data is called trajectory data publishing.
Trajectory data publishing is central to location data analysis and has wide applications including urban planning, location-based services, intelligent vehicles, logistics, and others. Though the usefulness of such publishing is unquestionable, the trade-off being made is privacy of contributing users and control over data.
The privacy factor is equally important, considering that user location data is personal and sensitive. When it is possible to trace back the contributing user it might lead to unintended consequences that harms the safety and security of contributors. Equally important is the role of regulation and compliance becomes crucial. Hence data publishing should not violate user rights and preserve their privacy. In practice the aggregation is oblivious to the contributing user and hence the responsibility or preserving user privacy is pushed to the service provider or aggregator.